Question: Who is the {anion} for {conjugate base} of {sulfate ion}
Paraphrase: Who is the {anion} for {conjugate base} of {sulfate particle}
SPARQL (Wikidata):  select distinct ?sbj where { ?sbj wdt:P4149 wd:Q172290 . ?sbj wdt:P31 wd:Q107968 }